1. Field of the Invention
The present invention relates to a pointing device for moving a pointer or a cursor on a display of a computer to a desired position. In particular, the present invention relates to a pointing device which produces no positioning error of the pointer even though mechanical vibration or shock is added to the pointing device after determining a designated position of the pointer, so that the pointer is moved back to the designated position after the vibration or shock is over.
2. Description of the Related Art
Generally, data for operating a computer or carrying out application programs of the computer are processed by operating a keyboard of the computer. Recently, a pointing device such as a mouse or a digitizer comes into existence and its usefulness has been widely approved because of convenience of performing dialog operation between an operator and the computer.
The pointing device, which will be called a separated type pointing device hereinafter, such as the mouse or the digitizer is usually applied to a desk-type computer. However, when a portable computer such as a laptop type or a notebook type computer comes into existence, the separated type pointing device becomes inconvenient of use, because, it is hard to find a space for placing the separated type pointing device around the portable computer.
Then, a new type pointing device, which will be called an attached type pointing device hereinafter, such as a track-ball type, a tilting lever (or joystick) type or a sliding head type pointing device has been developed for the portable computer.
The attached type pointing device is mechanically attached to the keyboard, and does not require a space for operating the attached type pointing device around the portable computer. The attached type pointing device is also applied to an amusement computer generally called "game machine". In case of the amusement computer, a terminal box is usually used for remotely controlling the amusement computer. The attached type pointing device is mounted on the terminal box so that the attached type pointing device can be easily handled by anyone from a child to a man in any posture, sitting on a sofa or lying on a floor. The attached type pointing device consists of a supporting member and a manually actuating movable member, which will be simply called "movable member" hereinafter, mounted on the supporting member. The supporting member is for supporting the movable member and fixing the attached type pointing device to the keyboard or the terminal box. The movable member is provided for moving the pointer on the display by touching the movable member with a finger of the operator. The movable member can be moved freely in a limited zone. When the movable member is freed from the operator's touch, the movable member returns to a center position of the limited zone and stays there, and when the movable member is moved, the pointer is moved on the display in the same direction as the movable member at a speed proportional to a distance of the movable member moved from the center position.
In either case of the portable computer or the amusement computer, when the movable member is freed from operator's touch after the pointer has been positioned to a designated position on the display, it is desired that the pointer is fixed to the designated position and not affected by vibration or shock added to the pointing device and/or a change of a supporting posture of the pointing device against gravity.
In short, the attached type pointing device has been required to have a high return accuracy, producing no pointing error when the vibration or shock is added to the pointing device and/or the supporting posture of the pointing device is changed.
Typical pointing devices of the prior art are shown in FIGS. 1, 2, 3A, 3B and 3C. FIG. 1 is a schematic side view of a joystick type pointing device (100) of the prior art, FIG. 2 is a schematic side view of a sliding head type pointing device (200) of the prior art, and FIGS. 3A, 3B and 3C illustrate typical returning mechanisms of the prior art, applied to the movable member of the sliding head type pointing device 200 shown in FIG. 2.
The joystick type pointing device 100 shown in FIG. 1 is a typical attached type pointing device of the prior art applied to the amusement computer. The joystick type pointing device 100 consists of a lever (marked LEVER in the figure) (11), a close-coiled helical spring (SPRING) (13) inserted between a root of the LEVER 11 and a frame (FRAME) (12) on which the LEVER 11 is mounted, and a pointer coordinate detecting part (DET PART) (14) consisting of a light emitter (LIGHT EMITTER) (15) provided at a bottom tip of the LEVER 11 and a light receiver (LIGHT REC) (16) arranged on a printed circuit board (PCB) (17) located beneath the FRAME 12 directly opposite to the LIGHT EMITTER 15. The LIGHT REC 16 consists of a plurality of light detecting elements arranged in a matrix. For example, a Charge-Coupled Device (CCD) is used for the LIGHT REC 16. When the LEVER 11 is leaned against the force of the SPRING 13, the shaft of the LEVER 11 inclines, so that a direction of light radiated from the LIGHT EMITTER 15 is changed. Then, the light radiated from the LIGHT EMITTER 15 comes into designated light detecting elements. As a result, the designated light detecting elements produce electrical signals having information on a direction and a moving speed of the pointer.
However, when the joystick type pointing device is applied to the terminal box, there have been problems as follows.
1) Because of that the joystick type pointing device cannot be made small in size, the size of the terminal box becomes large. As a result, the terminal box must be held by both hands, causing a problem that the terminal box is hard to be held by children. PA1 2) When the LEVER 11 is freed from the operator's hand, a gravity center of the LEVER 11 is moved upward because of the characteristics of the SPRING 13. Therefore, there is a problem that when a supporting posture of the terminal equipment is changed, the LEVER 11 tends to incline due to terrestrial gravitation and vibrate due to a mechanical shock given to the terminal box. PA1 3) When the LEVER 11 having inclined is freed from the operator's hold, the LEVER 11 is going to return to a center position by the force of the SPRING 13. However, because of the characteristics of the SPRING 13, the LEVER 11 does not completely return to the center position, particularly when the inclination of the LEVER 11 is little. This produces a problem of decreasing the returning accuracy of the pointer, so that the pointer does not stay at the designated position and drifts inch by inch.
In order to solve the above problems, a new attached type pointing device called "sliding head type pointing device" has been developed. Regarding the sliding head type pointing device, Japanese Patent Publication 7-117876 and U.S. Pat. No. 5,504,502 are given to the same inventor Takashi Arita and others in Dec. 18, 1995 and Apr. 2, 1996 respectably.
FIG. 2 is a cross-sectional side view of the sliding head type pointing device 200 of the prior art. The sliding head type pointing device 200 consists of a sliding head (SLIDING HEAD) (21) as the movable member and a housing (HOUSING) (22) as the supporting member.
The SLIDING HEAD 21 has a round domed configuration consisting of a domed rubber part (RUBBER) (23) and a domed slider (SLIDER) (24) provided on an inner surface of the RUBBER 23. At a center of the RUBBER 23, there is an inward depressed portion into which a finger tip is inserted for sliding the SLIDING HEAD 21 on the HOUSING 22. At the inward depressed portion, there is a magnet holding part (25) in which a permanent magnet (MAGNET) (26) is buried so as to be placed at the center of the SLIDING HEAD 21. The SLIDING HEAD 21 is set on the HOUSING 22 so that the MAGNET 26 is brought in a central axis of the HOUSING 22 when the SLIDING HEAD 21 is freed. The MAGNET 26 is used for producing information on a position and moving speed of the pointer on the display. In order to produce the information, other kinds of elements such as optical elements may be used. Therefore, an element such as the MAGNET 26 can be called "pointer positioning element" generally.
The HOUSING 22 has round domed structure for mounting the SLIDING HEAD 21 and fitting the sliding head type pointing device 200 to the terminal box not depicted in FIG. 2. An upper surface of the HOUSING 22 is formed to a domed configuration so as to contact with the domed slider 24 of the SLIDING HEAD 21. The HOUSING 22 has an aperture at the center thereof for allowing the magnet holding part 25 to pass there through. In the HOUSING 22, a printed circuit board 28 is provided for wiring magnetically reluctant elements 27 and an electric switch 29.
At least two magnetically reluctant elements 27 are arranged on the printed circuit board 28, separated at equal distance from the central axis of the HOUSING 22 respectively. The magnetically reluctant elements 27 pick up a magnetic field of the MAGNET 26 respectively, producing electric signals regarding the position and moving speed of the pointer on the display. When the SLIDING HEAD 21 is slid, the magnetically reluctant elements 27 pick up the magnetic field respectively and produce electric signals in response to the slid direction and the slid amount of the SLIDING HEAD 21 from the central axis of the HOUSING 23. The electric signals from the magnetically reluctant elements 27 are processed for producing signals of the moving direction and speed of the pointer on the display. Namely, the moving direction and speed of the pointer are designated by the slid direction and distance of the SLIDING HEAD 21 from the central axis of the HOUSING 22 respectively. The magnetically reluctant elements 27 are for detecting the position and moving speed of the pointer on the display. Therefore, the magnetically reluctant elements 27 can be called "pointer co-ordinate position detectors" generally.
The electric switch 29 is mounted on the PCB 28 so as to be on the central axis of the HOUSING 22 for performing a click operation of the sliding head type pointing device 200. When the depressed portion of the RUBBER 23 is pushed down, the electric switch 29 is pushed so that the electric switch 29 performs the click operation.
Not depicted in FIG. 2, the sliding head type pointing device 200 has a mechanism for returning the SLIDING HEAD 21 to the center position when the SLIDING HEAD 21 is freed from the operator's finger. The mechanism will be called a "returning mechanism" hereinafter. FIGS. 3A, 3B and 3C show several types of returning mechanisms in the sliding head type pointing device 200 of the prior art. In FIG. 3A, a garter belt spring (GARTER-BELT SPRING) (33) having the configuration of a garter belt is hooked alternatively among a plurality of ("four" in FIG. 3A) poles (31 and 32) provided inside the SLIDING HEAD 21 and four on the HOUSING 22 respectively. By virtue of tensile strength of the GARTER BELT SPRING 33, the SLIDING HEAD 21 intends to return to the center position of the HOUSING 22 when the SLIDING HEAD 21 is freed. In FIG. 3B, instead of the GARTER BELT SPRING 33 used in FIG. 3A, a plurality of ("four" in FIG. 3B) straight springs (STRAIGHT SPRINGs) (36) having the same tensile strength are respectively hooked between hooks 31 and 32 neighbored to each other. By virtue of the tensile strength of the STRAIGHT SPRINGs 36, the SLIDING HEAD 21 intends to return to the center position when the SLIDING HEAD 21 is freed. In FIG. 3C, in order to couple the SLIDING HEAD 21 with the HOUSING 22, a coil-forced spring (COIL SPRING) (35) is provided between the SLIDING HEAD 21 and a spring holder (34) provided to the HOUSING 22 along the central axis of the HOUSING 22. By virtue of the restoring force of the COIL SPRING 35, the SLIDING HEAD 21 intends to return to the center position when the SLIDING HEAD 21 is freed.
Thus, when the SLIDING HEAD 21 is freed, the SLIDING HEAD 21 intends to return to the center position on the central axis of the HOUSING 22 by the returning mechanism. However, in either case of FIGS. 3A, 3B or FIG. 3C, since the spring is laid between the SLIDING HEAD 21 and the HOUSING 22, the SLIDING HEAD 21 is returned to the center position only by the restoring force of the spring. Therefore, if the restoring force of the spring is strengthened, the SLIDING HEAD 21 becomes hard to be handled, and if the restoring force of the spring is weakened, the SLIDING HEAD 21 becomes hard to be returned. In particular, when the SLIDING HEAD 21 is slid a small amount, the SLIDING HEAD 21 is hard to be returned to the center position. Since the sliding head type pointing device has been a representative attached type pointing device, it can be concluded that the returning accuracy of the attached type pointing device has been low in the prior art.
As described with reference to FIG. 2, the moving direction and speed of the pointer on the display can be changed in any value in an analog fashion. Namely, the MAGNET 26 and the magnetically reluctant elements 27 formulate analog pointing system in compliance with analog pointing software. However, there is other pointing system called digital pointing system operating under digital pointing software. The digital pointing system is required for, for example, a high speed game. In case of the digital pointing system, the pointer moves on the display digitally a predetermined distance every step, in a predetermined direction such as up, down, right, left or diagonal direction of those. Therefore, in the digital pointing system, only a switching function is enough to move the pointer. As a result, in order to operate both the analog pointing system and the digital pointing system with one terminal box, another pointing device called "switching type pointing device" is required to be added to the terminal box for the digital pointing system. This causes troubles that the terminal box becomes complex in operation and large in size.